Interleukin 12 (IL-12) is known to effect immune function in various disease states. In vitro data suggest that IL-12 alters the balance of type 1 and 2 T helper (Th1/Th2) responses in PBMC from HIV-seropositive persons. We will test this hypothesis in vivo. Three different doses of rhIL-12 will be given to HIV-seropositive persons twice per week for 12 weeks. Measurements of HIV replication (HIV RNA by branched chain DNA assay) and immune function (plasma IFN(, CTL activity and Th1/Th2 responses of ex vivo-stimulated PBMC from IL-12 treated patients), as well as pharmacokinetic measurements, will be obtained. We will therefore obtain preliminary data showing whether IL-12 decreases HIV replication or has beneficial effects on immune function in HIV-seropositive persons.